The present invention relates to a waveguide antenna output for a planar antenna comprising an array of radiating or receiving elements for high-frequency signals. It also relates to a system for transmitting or receiving high-frequency signals, comprising a planar antenna having such an antenna output, used in systems for receiving 12 GHz television signals, more specifically television signals transmitted by geostationary satellites.
The two French Patent Applications No. 81 08 780 (corresponding to U.S. Pat. No. 4,486,758) and No. 82 04 252 (corresponding to U.S. Pat. No. 4,527,165), published by Applicants on May 4, 1981 and Mar. 12, 1982, respectively both describe a high-frequency planar antenna comprising an array of radiating or receiving elements. The first of the French patent applications relates to an antenna whose elements are formed on the one hand from three insulating sheets in which miniature horns of a square or a rectangular cross-section are provided and whose inside surface is metal-plated and on the other hand from two supply networks arranged between these respective sheets for receiving signals propagating in the miniature horns. The second patent application relates to an antenna which is likewise formed from three sheets and two supply networks but in which, to put it more precisely, the elements have a first layer with a first cavity, first and second networks of high-frequency transmission lines situated on both sides of this first layer and coupled for the reception of signals to each cavity along two perpendicular axes, (but in parallel with the respective elements) and on the other side of both supply networks second and third layers having cavities corresponding to the first cavities, the three layers or sheets thus provided being made of metal or of a dielectric material with metal-plated walls of the cavities penetrating them. In both these applications the cavities in the sheet or rear layer are inter alia short-circuited, at a depth which is generally near .lambda./4.
The structures described in the two above-mentioned documents have however the disadvantage that the supply networks which take off the signals propagating in the cavities are not in the same plane but are remote from each other for a distance equal to the width of the first sheet and that this arrangement causes a phase shift between the signals received by either the one or the other of these networks. This width and consequently the phase shift may be reduced, but only to a very small extent, when the transmission line networks are provided with grooves for guiding the central conductors of these lines as is disclosed in the second of the above-mentioned applications.